NORAH O'DONNELL: Wendy Davis was a little-known Democratic state senator in Texas. But her marathon defense of abortion rights drew national attention. And today, Davis announced she's running for governor.

MANUEL BOJORQUEZ (voice-over): The early odds are against Wendy Davis. It's been nearly 20 years since Texas voters put a Democrat in statewide office. The state senator stepped into the national spotlight with pink sneakers, during a 13-hour filibuster of new abortion restrictions here.

Democrats have become hopeful about Texas, because its demographics are shifting. By 2025, the percentage of white voters may drop below fifty percent, and the percentage of Hispanic voters may rise from 26 to as much as 44 percent. Democrat gains here could influence American politics. The state has 26 Republican members of Congress.